In many industrial and clinical environments, it is desirable to deliver a gas-enriched fluid to a site of interest, and/or increase the gas concentration of a fluid without a significant increase in the fluid volume.
For example, a fire may be extinguished by delivering an inflammable or an inert gas, such as carbon dioxide or nitrogen, rapidly to the fire via a fluid transporting medium. Environmental problems presented by toxic site cleanups may be ameliorated by delivering a high concentration of a neutralizing or cleansing gaseous agent to the toxic site. The oxygenation level of ponds used in fish farms, and the oxygenation level of waste streams (prior to their release into the environment) may also be increased by delivery of oxygen-enriched fluids to the ponds or streams.
One method of obtaining an increase in the gas concentration level without significant increase in fluid volume is by directly pumping a desired gas into a fluid site of interest. However, such direct pumping is not always efficient and may thereby result in an insufficient increase in gas concentration. Where a noxious gas is used, direct pumping also poses waste engineering problems and/or health hazard due to the presence of any unabsorbed noxious gas.
Another method of obtaining an increase in the gas concentration level without significant increase in fluid volume is by infusing a gas-enriched fluid, such as a gas-supersaturated fluid, into the site of interest. To create a gas-supersaturated fluid, high pressure compression of a gas-liquid mixture can be performed, for example, with the use of a high pressure gas exchanger. Prior art systems for producing gas-supersaturated fluids typically require the use of a high pressure vessel to provide dwell time for dissolving gas nuclei in the fluid outputted from the high pressure gas exchanger. Two such prior art systems are U.S. Pat. No. 5,407,426, "Method and Apparatus For Delivering Oxygen Into Blood" to Spears and U.S. Pat. No. 5,569,180, "Method For Delivering A Gas-Supersaturated Fluid To A Gas-Depleted Site And Use Thereof" to Spears.
In addition, gas nuclei may be present in the fluid prior to supersaturating the fluid with gas. For example, gas nuclei may be dust particles suspended in the fluid or crevices in the container wall in which gas is trapped or absorbed. The presence of gas nuclei facilitates cavitation inception (or, bubble formation), resulting in release of gas from the liquid and thereby decreasing the gas concentration of the fluid.
Furthermore, some prior art systems also require a high pressure (&gt;70 bar) fluid pump to deliver the gas-supersaturated fluid. Particularly in industrial applications (where it may be necessary to deliver large volumes of a gas-enriched fluid to a site of interest), such prior art systems may prove impractical because of the overall complexity, cost, and time associated with operating them.
Another problem associated some of the prior art devices in infusing gas-supersaturated fluid from a high pressure vessel into a site of interest is that cavitation inception at or near the exit ports often results. Cavitation inception may occur because ejection of the fluid into an atmospheric environment results in a decrease in the hydrostatic pressure of the fluid below the gas partial pressure. Disturbances at or near the exit ports may further facilitate cavitation inception. When cavitation takes place, gas is released from the fluid, decreasing its gas concentration. Furthermore, the presence of bubbles in the fluid generates turbulence and impedes the flow of the fluid beyond the exit ports.
Accordingly, there remains a need in the art for a simple, efficient and cost-effective system and method for producing and delivering gas-supersaturated fluid to a site of interest which does not require a high pressure vessel to provide dwell time and which does not require a high pressure fluid pump for delivery of the gas-supersaturated fluid. There remains a further need for a system and method for producing and delivering gas-supersaturated fluid to a site of interest without cavitation inception in the fluid during ejection, particularly at or near the exit ports.